mirror of
https://github.com/ganelson/inform.git
synced 2024-07-07 17:44:22 +03:00
119 lines
4.8 KiB
OpenEdge ABL
119 lines
4.8 KiB
OpenEdge ABL
[CReferences::] C References.
|
|
|
|
How changes to storage objects are translated into C.
|
|
|
|
@ References identify storage objects which are being written to or otherwise
|
|
modified, rather than having their current contents read.
|
|
|
|
There are seven possible ways to modify something identified by a reference,
|
|
and we need constants to identify these ways in the code we generate:
|
|
|
|
= (text to inform7_clib.h)
|
|
#define i7_lvalue_SET 1
|
|
#define i7_lvalue_PREDEC 2
|
|
#define i7_lvalue_POSTDEC 3
|
|
#define i7_lvalue_PREINC 4
|
|
#define i7_lvalue_POSTINC 5
|
|
#define i7_lvalue_SETBIT 6
|
|
#define i7_lvalue_CLEARBIT 7
|
|
=
|
|
|
|
@ Those seven ways correspond to seven Inter primitives, with the following
|
|
signatures:
|
|
= (text)
|
|
primitive !store ref val -> val
|
|
primitive !preincrement ref -> val
|
|
primitive !postincrement ref -> val
|
|
primitive !predecrement ref -> val
|
|
primitive !postdecrement ref -> val
|
|
primitive !setbit ref val -> void
|
|
primitive !clearbit ref val -> void
|
|
=
|
|
Since C functions can have their return values freely ignored, we will in fact
|
|
implement |!setbit| and |!clearbit| as if they too had the signature
|
|
|ref val -> val|.
|
|
|
|
=
|
|
int CReferences::invoke_primitive(code_generation *gen, inter_ti bip, inter_tree_node *P) {
|
|
text_stream *OUT = CodeGen::current(gen);
|
|
text_stream *store_form = NULL;
|
|
switch (bip) {
|
|
case STORE_BIP: store_form = I"i7_lvalue_SET"; break;
|
|
case PREINCREMENT_BIP: store_form = I"i7_lvalue_PREINC"; break;
|
|
case POSTINCREMENT_BIP: store_form = I"i7_lvalue_POSTINC"; break;
|
|
case PREDECREMENT_BIP: store_form = I"i7_lvalue_PREDEC"; break;
|
|
case POSTDECREMENT_BIP: store_form = I"i7_lvalue_POSTDEC"; break;
|
|
case SETBIT_BIP: store_form = I"i7_lvalue_SETBIT"; break;
|
|
case CLEARBIT_BIP: store_form = I"i7_lvalue_CLEARBIT"; break;
|
|
default: return NOT_APPLICABLE;
|
|
}
|
|
if (store_form) @<This does indeed modify a value by reference@>;
|
|
return FALSE;
|
|
}
|
|
|
|
@ Some storage objects, like variables, can be generated to C code which works
|
|
in either an lvalue or rvalue context. For example, the Inter variable |frog|
|
|
generates just as the C variable |i7_mgl_frog|.[1] It's then fine to generate
|
|
code like either |10 + i7_mgl_frog|, where it is used in a |val| context, or
|
|
like |i7_mgl_frog++|, where it is used in a |ref| context.
|
|
|
|
But other storage objects are not so lucky, and can only be written to by
|
|
calling functions.
|
|
|
|
[1] In real life, do not mangle frogs. See C. S. Lewis, "Perelandra", 1943.
|
|
|
|
@<This does indeed modify a value by reference@> =
|
|
inter_tree_node *ref = InterTree::first_child(P);
|
|
inter_tree_node *storage_ref = InterTree::first_child(P);
|
|
if (storage_ref->W.instruction[0] == REFERENCE_IST)
|
|
storage_ref = InterTree::first_child(storage_ref);
|
|
int val_supplied = FALSE;
|
|
if ((bip == STORE_BIP) || (bip == SETBIT_BIP) || (bip == CLEARBIT_BIP)) val_supplied = TRUE;
|
|
if (ReferenceInstruction::node_is_ref_to(gen->from, ref, LOOKUP_BIP))
|
|
@<This is a reference to a word lookup@>
|
|
else if (ReferenceInstruction::node_is_ref_to(gen->from, ref, LOOKUPBYTE_BIP))
|
|
@<This is a reference to a byte lookup@>
|
|
else if (ReferenceInstruction::node_is_ref_to(gen->from, ref, PROPERTYVALUE_BIP))
|
|
@<This is a reference to a property value@>
|
|
else
|
|
@<This is a reference to something else@>;
|
|
|
|
@<This is a reference to a word lookup@> =
|
|
WRITE("(");
|
|
WRITE("i7_change_word(proc, ");
|
|
Vanilla::node(gen, InterTree::first_child(storage_ref)); WRITE(", ");
|
|
Vanilla::node(gen, InterTree::second_child(storage_ref)); WRITE(", ");
|
|
if (val_supplied) { VNODE_2C; } else { WRITE("0"); }
|
|
WRITE(", %S", store_form);
|
|
WRITE("))");
|
|
|
|
@<This is a reference to a byte lookup@> =
|
|
WRITE("(");
|
|
WRITE("i7_change_byte(proc, ");
|
|
Vanilla::node(gen, InterTree::first_child(storage_ref)); WRITE(" + ");
|
|
Vanilla::node(gen, InterTree::second_child(storage_ref)); WRITE(", ");
|
|
if (val_supplied) { VNODE_2C; } else { WRITE("0"); }
|
|
WRITE(", %S", store_form);
|
|
WRITE("))");
|
|
|
|
@<This is a reference to a property value@> =
|
|
WRITE("(");
|
|
WRITE("i7_change_gprop_value(proc, ");
|
|
Vanilla::node(gen, InterTree::first_child(storage_ref)); WRITE(", ");
|
|
Vanilla::node(gen, InterTree::second_child(storage_ref)); WRITE(", ");
|
|
Vanilla::node(gen, InterTree::third_child(storage_ref)); WRITE(", ");
|
|
if (val_supplied) { VNODE_2C; } else { WRITE("0"); }
|
|
WRITE(", %S", store_form);
|
|
WRITE("))");
|
|
|
|
@<This is a reference to something else@> =
|
|
switch (bip) {
|
|
case PREINCREMENT_BIP: WRITE("++("); VNODE_1C; WRITE(")"); break;
|
|
case POSTINCREMENT_BIP: WRITE("("); VNODE_1C; WRITE(")++"); break;
|
|
case PREDECREMENT_BIP: WRITE("--("); VNODE_1C; WRITE(")"); break;
|
|
case POSTDECREMENT_BIP: WRITE("("); VNODE_1C; WRITE(")--"); break;
|
|
case STORE_BIP: WRITE("("); VNODE_1C; WRITE(" = "); VNODE_2C; WRITE(")"); break;
|
|
case SETBIT_BIP: VNODE_1C; WRITE(" = "); VNODE_1C; WRITE(" | "); VNODE_2C; break;
|
|
case CLEARBIT_BIP: VNODE_1C; WRITE(" = "); VNODE_1C; WRITE(" &~ ("); VNODE_2C; WRITE(")"); break;
|
|
}
|